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Author Topic: R 2005D Motorola service monitor help  (Read 7599 times)
N3DT
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Posts: 560




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« Reply #15 on: November 23, 2012, 01:33:54 PM »

The schematic did help.  I was thinking one of the TPs was at ground, but the track just looked like it went to ground.  Schematic confirmed that it was not at ground and when I removed some parts and traced the track it was apparent there was a short to ground.  And any shorted supply will shut the whole thing down.  I was pretty sure it was a power problem since there were no voltages anywhere.
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K7LZR
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Posts: 25




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« Reply #16 on: November 28, 2012, 02:26:53 PM »

Hope that's all it was. I used an R2014D for a long time, loved it. Now I use an HP 8924c, which is a very capable lab-quality instrument but must stay on the bench cuz it weighs 59 Lbs.!!!

- Darrell/K7LZR (formerly KA7BTV)
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N3DT
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Posts: 560




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« Reply #17 on: December 01, 2012, 07:15:03 PM »

The diodes got rid of the short on the A5 board, but it's still not working.  I've been printing out the circuits of the individual boards, and the block diagram of the power supply, but there are voltages missing that appear to be shut off from the control board, and that one is very hard to figure.  I'm still hoping it's something in one of the power supply boards and not the control board.  I've got big pages of schematics and diagrams all over the work area trying to sort through it.  This may take a while.  There are plenty of mistakes in the book too that I've been going through and correcting.  Not unusual from what I've seen in the past.

I still need to try the DC supply and will do that next.  It may be the AC switching FETs.

Dave
N3DT
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N3DT
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Posts: 560




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« Reply #18 on: December 03, 2012, 05:51:34 PM »

The DC input doesn't work either.  I'm getting more and more convinced that the A4 Control Board is shutting things down for some reason.  I need to make an extension board so I can trouble shoot the board with voltages on it.  I'm going nowhere shooting in the dark.
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KE3WD
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« Reply #19 on: December 04, 2012, 05:05:05 AM »

Can you disconnect boards one at a time and then check to see if power comes up on the dead lines from power supply? 
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K4JJL
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Posts: 498




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« Reply #20 on: December 04, 2012, 08:26:51 AM »

I would think a shorted diode would blow a fuse.  Did you check all those?

Also, I had a mica capacitor short and explode inside a 2001D.  Horrible smell.  Might check for some of those gone bad, too.
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N3DT
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Posts: 560




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« Reply #21 on: December 14, 2012, 06:39:40 AM »

I've found a bad LM339 comparator on the A4 Control board, the AC/DC overcurrent circuit.  It's shutting down the PWM on the shutdown pin.  I've got some parts on order, but when I replace the 339 I want to add a socket, so I'm waiting for that.

I've got all the extra boards pulled up and if this gets the PS working, I'll put the boards in one by one, but we'll see.
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KA5IPF
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« Reply #22 on: December 14, 2012, 08:13:02 AM »

Never use a socket. The odds are the socket will cause problems long before the IC will fail again.

My 2 cents.

Clif
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NJ1K
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Posts: 331




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« Reply #23 on: December 14, 2012, 09:28:51 AM »

I have never had a chip socket fail....
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N3DT
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Posts: 560




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« Reply #24 on: December 14, 2012, 06:55:38 PM »

Well, I didn't get cheap sockets, I got the open frame Aries sockets with solid gold contacts.  16-3518-10  I'm sure they will be good.
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KE3WD
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« Reply #25 on: December 15, 2012, 07:20:34 AM »

"Never say, 'never'"...

<g>
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NJ1K
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Posts: 331




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« Reply #26 on: December 15, 2012, 08:14:49 AM »

"Never say, 'never'"...

<g>

So, out of the hundreds of millions of sockets in use out there, what percentage of these sockets might have caused problems?  And if they are such a problem, why do thousands of manufacturers still use them?  Oh, I suppose if one submerged the board in water, the socket might likely fail before the chip actually does, but I don't usually submerge my circuit board in water. 
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KE3WD
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« Reply #27 on: December 15, 2012, 12:29:56 PM »

NJ1K --  You weren't the first to use the word in this thread, and I wasn't pointing that at you.

If the man wants to socket the board, that's fine with me, have done the same *many* times myself.


73
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WB6DGN
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Posts: 619




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« Reply #28 on: December 15, 2012, 12:37:59 PM »

Quote
Never use a socket. The odds are the socket will cause problems long before the IC will fail again.

There was a time when that was pretty generally true but, as the OP noted, there are quality sockets available.  Especially in this case where he expressed some uncertainty whether he'd found the whole problem.  If he didn't and the IC failed again, he'd be tempting fate by having to remove it again to replace it a second time, especially if he's not using a vacuum desoldering tool.  In this case, I think his choice is a good one.  There are times when a socket is still not a good choice such as with very high frequency signals but that is not the case here.  Good luck with it.  I used a version of that monitor for the last eight years before I retired.  When they're working right and have a good bright CRT, I think they're an excellent monitor; heads above the 2200/2400/2600 series.  That's why I wouldn't let them exchange mine for a newer one.
Tom
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N3DT
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Posts: 560




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« Reply #29 on: December 15, 2012, 01:23:11 PM »

When our agency went digital, there was no use for the R2005D.  That's where the 2600 series shine.  There was even automated testing using the later models but they were too cheap to buy the software.

Yes, I'm not sure the 339 is the only problem, so any other bad chips get the socket treatment too.
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